The established technique for hydrolyzing unactivated haloaromatic compounds to phenolic compounds is to contact the haloaromatic compounds with dilute aqueous solutions of alkali metal hydroxides at temperatures under about 400.degree. C. Copper catalysts are used to increase the yield of unrearranged products. The potential value of using more concentrated hydroxide solutions has been recognized (U.S. Pat. No. 3,440,290), but even studies which explored the effect of base concentration on the aqueous hydrolysis of non-phenolic haloaromatic compounds were limited to 36% caustic. (Ind. Eng. Chem., 38 254-261 (1946); J. Am. Chem. Soc., 79 1458-1462 (1957).) More concentrated hydroxide solutions or lower temperatures can be used for hydrolysis of halophenols than for non-phenolic haloaromatic compounds. Likewise, alcohol or glycol solvents are known to permit the use of stronger bases or lower temperatures for the hydrolysis of haloaromatic compounds. (See U.S. Pat. Nos. 2,126,648; 2,644,015.) The use of concentrated aqueous base in the hydrolysis requires higher temperatures than are necessary with dilute bases, and these conditions result in an increase of dimeric products such as diaryl phenols and diaryl ethers. (See German Pat. No. 1,930,341.)